diff options
Diffstat (limited to 'minzip/Hash.c')
| -rw-r--r-- | minzip/Hash.c | 390 |
1 files changed, 0 insertions, 390 deletions
diff --git a/minzip/Hash.c b/minzip/Hash.c deleted file mode 100644 index 8c6ca9b..0000000 --- a/minzip/Hash.c +++ /dev/null @@ -1,390 +0,0 @@ -/* - * Copyright 2006 The Android Open Source Project - * - * Hash table. The dominant calls are add and lookup, with removals - * happening very infrequently. We use probing, and don't worry much - * about tombstone removal. - */ -#include <stdlib.h> -#include <assert.h> - -#define LOG_TAG "minzip" -#include "Log.h" -#include "Hash.h" - -/* table load factor, i.e. how full can it get before we resize */ -//#define LOAD_NUMER 3 // 75% -//#define LOAD_DENOM 4 -#define LOAD_NUMER 5 // 62.5% -#define LOAD_DENOM 8 -//#define LOAD_NUMER 1 // 50% -//#define LOAD_DENOM 2 - -/* - * Compute the capacity needed for a table to hold "size" elements. - */ -size_t mzHashSize(size_t size) { - return (size * LOAD_DENOM) / LOAD_NUMER +1; -} - -/* - * Round up to the next highest power of 2. - * - * Found on http://graphics.stanford.edu/~seander/bithacks.html. - */ -unsigned int roundUpPower2(unsigned int val) -{ - val--; - val |= val >> 1; - val |= val >> 2; - val |= val >> 4; - val |= val >> 8; - val |= val >> 16; - val++; - - return val; -} - -/* - * Create and initialize a hash table. - */ -HashTable* mzHashTableCreate(size_t initialSize, HashFreeFunc freeFunc) -{ - HashTable* pHashTable; - - assert(initialSize > 0); - - pHashTable = (HashTable*) malloc(sizeof(*pHashTable)); - if (pHashTable == NULL) - return NULL; - - pHashTable->tableSize = roundUpPower2(initialSize); - pHashTable->numEntries = pHashTable->numDeadEntries = 0; - pHashTable->freeFunc = freeFunc; - pHashTable->pEntries = - (HashEntry*) calloc((size_t)pHashTable->tableSize, sizeof(HashTable)); - if (pHashTable->pEntries == NULL) { - free(pHashTable); - return NULL; - } - - return pHashTable; -} - -/* - * Clear out all entries. - */ -void mzHashTableClear(HashTable* pHashTable) -{ - HashEntry* pEnt; - int i; - - pEnt = pHashTable->pEntries; - for (i = 0; i < pHashTable->tableSize; i++, pEnt++) { - if (pEnt->data == HASH_TOMBSTONE) { - // nuke entry - pEnt->data = NULL; - } else if (pEnt->data != NULL) { - // call free func then nuke entry - if (pHashTable->freeFunc != NULL) - (*pHashTable->freeFunc)(pEnt->data); - pEnt->data = NULL; - } - } - - pHashTable->numEntries = 0; - pHashTable->numDeadEntries = 0; -} - -/* - * Free the table. - */ -void mzHashTableFree(HashTable* pHashTable) -{ - if (pHashTable == NULL) - return; - mzHashTableClear(pHashTable); - free(pHashTable->pEntries); - free(pHashTable); -} - -#ifndef NDEBUG -/* - * Count up the number of tombstone entries in the hash table. - */ -static int countTombStones(HashTable* pHashTable) -{ - int i, count; - - for (count = i = 0; i < pHashTable->tableSize; i++) { - if (pHashTable->pEntries[i].data == HASH_TOMBSTONE) - count++; - } - return count; -} -#endif - -/* - * Resize a hash table. We do this when adding an entry increased the - * size of the table beyond its comfy limit. - * - * This essentially requires re-inserting all elements into the new storage. - * - * If multiple threads can access the hash table, the table's lock should - * have been grabbed before issuing the "lookup+add" call that led to the - * resize, so we don't have a synchronization problem here. - */ -static bool resizeHash(HashTable* pHashTable, int newSize) -{ - HashEntry* pNewEntries; - int i; - - assert(countTombStones(pHashTable) == pHashTable->numDeadEntries); - //LOGI("before: dead=%d\n", pHashTable->numDeadEntries); - - pNewEntries = (HashEntry*) calloc(newSize, sizeof(HashTable)); - if (pNewEntries == NULL) - return false; - - for (i = 0; i < pHashTable->tableSize; i++) { - void* data = pHashTable->pEntries[i].data; - if (data != NULL && data != HASH_TOMBSTONE) { - int hashValue = pHashTable->pEntries[i].hashValue; - int newIdx; - - /* probe for new spot, wrapping around */ - newIdx = hashValue & (newSize-1); - while (pNewEntries[newIdx].data != NULL) - newIdx = (newIdx + 1) & (newSize-1); - - pNewEntries[newIdx].hashValue = hashValue; - pNewEntries[newIdx].data = data; - } - } - - free(pHashTable->pEntries); - pHashTable->pEntries = pNewEntries; - pHashTable->tableSize = newSize; - pHashTable->numDeadEntries = 0; - - assert(countTombStones(pHashTable) == 0); - return true; -} - -/* - * Look up an entry. - * - * We probe on collisions, wrapping around the table. - */ -void* mzHashTableLookup(HashTable* pHashTable, unsigned int itemHash, void* item, - HashCompareFunc cmpFunc, bool doAdd) -{ - HashEntry* pEntry; - HashEntry* pEnd; - void* result = NULL; - - assert(pHashTable->tableSize > 0); - assert(item != HASH_TOMBSTONE); - assert(item != NULL); - - /* jump to the first entry and probe for a match */ - pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)]; - pEnd = &pHashTable->pEntries[pHashTable->tableSize]; - while (pEntry->data != NULL) { - if (pEntry->data != HASH_TOMBSTONE && - pEntry->hashValue == itemHash && - (*cmpFunc)(pEntry->data, item) == 0) - { - /* match */ - //LOGD("+++ match on entry %d\n", pEntry - pHashTable->pEntries); - break; - } - - pEntry++; - if (pEntry == pEnd) { /* wrap around to start */ - if (pHashTable->tableSize == 1) - break; /* edge case - single-entry table */ - pEntry = pHashTable->pEntries; - } - - //LOGI("+++ look probing %d...\n", pEntry - pHashTable->pEntries); - } - - if (pEntry->data == NULL) { - if (doAdd) { - pEntry->hashValue = itemHash; - pEntry->data = item; - pHashTable->numEntries++; - - /* - * We've added an entry. See if this brings us too close to full. - */ - if ((pHashTable->numEntries+pHashTable->numDeadEntries) * LOAD_DENOM - > pHashTable->tableSize * LOAD_NUMER) - { - if (!resizeHash(pHashTable, pHashTable->tableSize * 2)) { - /* don't really have a way to indicate failure */ - LOGE("Dalvik hash resize failure\n"); - abort(); - } - /* note "pEntry" is now invalid */ - } else { - //LOGW("okay %d/%d/%d\n", - // pHashTable->numEntries, pHashTable->tableSize, - // (pHashTable->tableSize * LOAD_NUMER) / LOAD_DENOM); - } - - /* full table is bad -- search for nonexistent never halts */ - assert(pHashTable->numEntries < pHashTable->tableSize); - result = item; - } else { - assert(result == NULL); - } - } else { - result = pEntry->data; - } - - return result; -} - -/* - * Remove an entry from the table. - * - * Does NOT invoke the "free" function on the item. - */ -bool mzHashTableRemove(HashTable* pHashTable, unsigned int itemHash, void* item) -{ - HashEntry* pEntry; - HashEntry* pEnd; - - assert(pHashTable->tableSize > 0); - - /* jump to the first entry and probe for a match */ - pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)]; - pEnd = &pHashTable->pEntries[pHashTable->tableSize]; - while (pEntry->data != NULL) { - if (pEntry->data == item) { - //LOGI("+++ stepping on entry %d\n", pEntry - pHashTable->pEntries); - pEntry->data = HASH_TOMBSTONE; - pHashTable->numEntries--; - pHashTable->numDeadEntries++; - return true; - } - - pEntry++; - if (pEntry == pEnd) { /* wrap around to start */ - if (pHashTable->tableSize == 1) - break; /* edge case - single-entry table */ - pEntry = pHashTable->pEntries; - } - - //LOGI("+++ del probing %d...\n", pEntry - pHashTable->pEntries); - } - - return false; -} - -/* - * Execute a function on every entry in the hash table. - * - * If "func" returns a nonzero value, terminate early and return the value. - */ -int mzHashForeach(HashTable* pHashTable, HashForeachFunc func, void* arg) -{ - int i, val; - - for (i = 0; i < pHashTable->tableSize; i++) { - HashEntry* pEnt = &pHashTable->pEntries[i]; - - if (pEnt->data != NULL && pEnt->data != HASH_TOMBSTONE) { - val = (*func)(pEnt->data, arg); - if (val != 0) - return val; - } - } - - return 0; -} - - -/* - * Look up an entry, counting the number of times we have to probe. - * - * Returns -1 if the entry wasn't found. - */ -int countProbes(HashTable* pHashTable, unsigned int itemHash, const void* item, - HashCompareFunc cmpFunc) -{ - HashEntry* pEntry; - HashEntry* pEnd; - int count = 0; - - assert(pHashTable->tableSize > 0); - assert(item != HASH_TOMBSTONE); - assert(item != NULL); - - /* jump to the first entry and probe for a match */ - pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)]; - pEnd = &pHashTable->pEntries[pHashTable->tableSize]; - while (pEntry->data != NULL) { - if (pEntry->data != HASH_TOMBSTONE && - pEntry->hashValue == itemHash && - (*cmpFunc)(pEntry->data, item) == 0) - { - /* match */ - break; - } - - pEntry++; - if (pEntry == pEnd) { /* wrap around to start */ - if (pHashTable->tableSize == 1) - break; /* edge case - single-entry table */ - pEntry = pHashTable->pEntries; - } - - count++; - } - if (pEntry->data == NULL) - return -1; - - return count; -} - -/* - * Evaluate the amount of probing required for the specified hash table. - * - * We do this by running through all entries in the hash table, computing - * the hash value and then doing a lookup. - * - * The caller should lock the table before calling here. - */ -void mzHashTableProbeCount(HashTable* pHashTable, HashCalcFunc calcFunc, - HashCompareFunc cmpFunc) -{ - int numEntries, minProbe, maxProbe, totalProbe; - HashIter iter; - - numEntries = maxProbe = totalProbe = 0; - minProbe = 65536*32767; - - for (mzHashIterBegin(pHashTable, &iter); !mzHashIterDone(&iter); - mzHashIterNext(&iter)) - { - const void* data = (const void*)mzHashIterData(&iter); - int count; - - count = countProbes(pHashTable, (*calcFunc)(data), data, cmpFunc); - - numEntries++; - - if (count < minProbe) - minProbe = count; - if (count > maxProbe) - maxProbe = count; - totalProbe += count; - } - - LOGI("Probe: min=%d max=%d, total=%d in %d (%d), avg=%.3f\n", - minProbe, maxProbe, totalProbe, numEntries, pHashTable->tableSize, - (float) totalProbe / (float) numEntries); -} |